Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/48—Isomerisation; Cyclisation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/14—Peroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B11/00—Layered products comprising a layer of bituminous or tarry substances
  • B32B11/10—Layered products comprising a layer of bituminous or tarry substances next to a fibrous or filamentary layer
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/13—Phenols; Phenolates
  • C08K5/134—Phenols containing ester groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene

Definitions

• the technical field relates to a process for producing high melt strength polypropylene (HMS-PP).
• WO 99/027007 discloses a process which involves thermal treatment of polypropylene with a peroxydicarbonate.
• peroxydicarbonates including dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, and di(4-tert-butylcyclohexyl) peroxydicarbonate.
• dialkyl peroxydicarbonates are, apart from their good performance in the process, their safety aspects and ease of handling. All of them are in solid form and—in contrast to many other peroxydicarbonates—can be safely stored and handled at room temperature. In addition, they can be used in an extrusion process.
• High melt strength polypropylene finds use in food packaging and automotive applications.
• the alcoholic decomposition product may evaporate and condense on the package's lid or the microwave window, thereby negatively affecting their transparency.
• HMS-PP used in automotive interiors may heat up at warm weather conditions and the alcoholic decomposition product may condense on the car windows, with the evidently undesired result of reduced visibility.
• the decomposition products of dicetyl and dimyristyl peroxydicarbonates also tend to migrate to the surface of the modified polypropylene. This phenomenon is called “blooming” and leads to the formation of white or glittering particles on the surface, resulting in a non-uniform appearance of the polymer surface.
• a process for enhancing the melt strength of polypropylene includes extruding a polypropylene in a twin-screw extruder, under inert atmosphere, at a temperature in the range of from about 150° C. to about 300° C., and in the presence of about 0.1 to about 3.0 wt %, based on the weight of the polypropylene, an organic peroxide with the formula
• each R is individually selected from C 1-5 alkyl groups.
• a process for enhancing the melt strength of polypropylene includes extruding a polypropylene in a twin-screw extruder, under inert atmosphere, at a temperature in the range of from about 160° C. to about 240° C., and in the presence of about 0.5 to about 2.0 wt %, based on the weight of the polypropylene, di(4-methylbenzoyl)peroxide.
• the word exemplary means serving as an example, instance, or illustration.
• the following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Any embodiment described herein as exemplary is not necessarily to be construed as preferred or advantageous over other embodiments.
• the embodiments described in this Detailed Description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope. Furthermore, there is no intention to be bound by any expressed or implied theory presented in this document.
• a process includes extruding the polypropylene in a twin-screw extruder, under inert atmosphere, using an organic peroxide of the formula
• each R is located at the para-position of the aromatic ring and is individually selected from C 1-5 alkyl groups.
• each R is individually selected from C 1-5 alkyl groups. Examples of such groups are methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, and tert-amyl. In another exemplary embodiment, each R is methyl.
• the organic peroxide is di(4-methylbenzoyl)peroxide.
• a process for enhancing the melt strength of polypropylene by extruding said polypropylene in a twin-screw extruder, under inert atmosphere, at a temperature between about 150° C. and about 300° C., and in the presence of about 0.1 to about 3.0 wt %, based on the weight of the polypropylene, of an organic peroxide as defined above.
• the polypropylene can be a homopolymer of propylene or a random, alternating, heterophasic, or block co- or terpolymer of propylene and other olefins.
• a propylene copolymer or terpolymer will contain one or more other olefins, such as ethylene, butene, pentene, hexene, heptene, or octene, but it may also comprise styrene or styrene derivatives.
• the content of olefins other than propylene is not more than about 30 wt % of all monomers.
• Polypropylene homopolymers and copolymers of propylene and ethylene are most preferred. It is also possible to use mixtures of polypropylene and polyethylene.
• the melting point of commercially available propylene homopolymer is about 160 to about 170° C.
• the melting point of propylene copolymers and terpolymers is generally lower.
• the molecular weight of the polypropylene contemplated herein can be selected from a wide range. Indicative of the molecular weight is the melt flow index (MFI). Use may be made of a polypropylene having an MFI from about 0.1 to about 1000 g/10 min (230° C., 21.6 N). In an embodiment, use is made of a polypropylene having an MFI from about 0.5 to about 250 g/10 min.
• MFI melt flow index
• the polypropylene may be a branched polypropylene, such as described in WO 2016/126429 and WO 2016/126430.
• the extrusion is performed at a temperature in the range of about 150 to about 300° C., for example, about 155 to about 250° C., such as about 160 to about 240° C.
• Extrusion is conducted under inert atmosphere, which means that it is conducted in an atmosphere of inert gas, such as nitrogen, carbon dioxide, or argon.
• inert gas such as nitrogen, carbon dioxide, or argon.
• nitrogen is used.
• oxygen concentration in the inert atmosphere is below about 1 vol %, for example, below about 0.5 vol %, such as below about 0.1 vol %.
• Extrusion allows modification of the polypropylene to be combined with pelletization.
• use is made of a twin-screw extruder. Single screw extruders are less suitable because they are unable to adequately homogenize the peroxide within the polypropylene.
• the residence time in the extruder is generally about 10 seconds to about 5 minutes.
• the screw speed of the extruder is in the range of about 25 to about 500 rpm, in an embodiment.
• the temperature of the extruder should be above the melting temperature of the polypropylene.
• the process contemplated herein can be carried out as a batch process, a continuous process, or a combination thereof.
• a continuous process is preferred.
• the organic peroxide is added to the polypropylene prior to or during extrusion.
• the organic peroxide to be used in the process contemplated herein is solid at room temperature and may be added to the polypropylene as a water-based formulation (suspension), as a solution, as a dispersion in an inert solvent such as isododecane, in the form of flakes, as a powder, as a wet powder formulation, or as a masterbatch in a polymer or on an inert solid carrier (e.g. silica), optionally in combination with anti-oxidants and/or acid catchers (e.g. calcium stearate).
• an inert solid carrier e.g. silica
• anti-oxidants and/or acid catchers e.g. calcium stearate
• vacuum or atmospheric degassing may be applied in order to remove volatile decomposition products and any water introduced as part of the peroxide formulation.
• organic peroxide to be used will depend on the desired degree of modification and on the type of polypropylene employed. In an embodiment, use is made of organic peroxide concentrations in the range of about 0.1 to about 3.0 g of peroxide per 100 g polypropylene, for example, in the range of about 0.5 to about 2.0 g per 100 g polypropylene; all calculated as pure and dry organic peroxide.
• Extrusion may be conducted in the presence of a co-agent in order to influence the melt flow index of the polypropylene and/or to enhance the degree of modification.
• coagents are TMAIC (trimethallyl isocyanurate), TAIC (triallyl isocyanurate), TAC (triallycyanurate), TRIM (trimethylol propane trimethacrylate), divinylbenzene, HVA-2 (N,N′-phenylene bismaleimide), AMSD (alpha methyl styrene dimer), and Perkalink 900 (1,3-bis(citraconimidomethyl)benzene).
• a co-agent is generally understood to be a polyfunctional reactive additive such as a polyunsaturated compound which will react rapidly with polymer radicals, will overcome steric hindrance and minimize undesirable side reactions.
• the incorporation of an effective amount of one or more of these co-agents into the polypropylene, prior to or during the process contemplated herein tends to influence the melt flow index and molecular weight of the resulting polypropylene.
• conventional adjuvants in an amount known to one skilled in the art, such as antioxidants, UV-stabilizers, lubricants, antidegradants, foaming agents, nucleating agents, fillers, pigments, acid catchers (e.g. calcium stearate), and/or antistatic agents may be added to the polypropylene.
• These adjuvants can be added to the polypropylene before as well as during or after extrusion.
• a chemical blowing agent e.g. azodicarbonamide
• a physical blowing agent e.g. a gas like nitrogen, carbon dioxide, butane, or isobutane
• a chemical blowing agent is preferably added before or after extrusion; a physical blowing agent is preferably injected during or after the extrusion.
• a stabilizer e.g. one or more antioxidants
• a stabilizer is added in order to deactivate any free radicals still present in the HMS-PP as well as any radicals which may be formed later from subsequent processing under air/oxygen.
• phr polypropylene
• the HMS-PP may be further processed as known to one of ordinary skill in the art. It may be formed directly into a desired end product, it may be processed using an underwater pelletizer, or it may be purified, modified, moulded, or blended with miscible amounts of other (polymer) materials, such as EPM, EPDM, and/or LDPE. Thus, there may be modifications using another polymer or monomer in order to enhance the end product's compatibility with other materials.
• the HMS-PP may be degraded to increase its processability and/or applicability or may be further processed by, for example, foaming, foam moulding, injection moulding, blow moulding, extrusion coating, profile extrusion, cast film extrusion, blown film extrusion, and/or thermoforming.
• the peroxide formulation was added in amounts corresponding to 10 g (2 phr) pure peroxide.
• the extruded material was led through a water bath for cooling and the cooled strands were granulated by an automatic granulator.
• melt-flow index MFI
• melt strength MS
• molecular weights branching number of the extruded HMS-PP compounds were analysed as described below. The results are listed in Table 1.
• the melt flow index (MFI) was measured with a Goettfert Melt Indexer MI-3 according to ISO 1133 (230° C./2.16 kg load). The MFI is expressed in g/10 min.
• the melt strength (MS) was measured (in cN) with a Goettfert Rheograph 20 (capillary rheometer) in combination with a Goettfert Rheotens 71.97, according to the manufacturer's instructions using the following configuration and settings:
• the molecular weight of the polymer was determined with High Temperature Size Exclusion Chromatography (HT-SEC) at 150° C.
• HT-SEC High Temperature Size Exclusion Chromatography
• the molecular weights of the samples i.e. the number-average (Mn), weight-average (Mw), and z-average (Mz) molecular weights, were calculated from Light Scattering (LS) detection.
• Branching numbers (Bn, i.e. the average number of branches per molecule) were calculated according to the theory of Zimm and Stockmayer, J. Chem. Phys. 17 (1949) 1301.
• a blank polypropylene sample i.e. a polypropylene treated in the same manner, but in the absence of peroxide—was used as reference.
• B n a calculation model of random, polydisperse, trifunctional branching was used with a structure factor ⁇ of 0.75.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Processes Of Treating Macromolecular Substances (AREA)

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